A study on ThO2–LaO1.5 solid solution: Lattice thermal expansion measurements and XPS studies

The lattice thermal expansion characteristics of ThO2–LaO1.5 solid solutions containing 18.5 and 47.6 mol% LaO1.5 were determined in the temperature range 298–1600 K by high temperature X-ray diffraction. The mean linear thermal expansion coefficients in this temperature range, for ThO2–LaO1.5 solid solutions are (11.89 and 14.09) × 10−6 K−1, respectively. The binding energies of Th 4f7/2 and La 3d5/2 energy levels of the solid solutions containing 12.9, 18.5, 27.9, 40.2, 47.6 and 50.3 mol% LaO1.5 were experimentally determined by X-ray photoelectron spectroscopy. These results suggested the presence of Th4+ and La3+ chemical states in the stoichiometric ThO2–LaO1.5 solid solutions.